Hi Maria, while I can't even begin to imagine what your illness is, the severe fatigue and stress are probably linked.
You are under severe stress, for one reason or another, and this puts a huge strain on the body as it fights it.
The fight or flight thing.
Sleep will be disrupted ,broken and not fulfilling, leaving you ill prepared to face the day, so more stress is generated from frustration and annoyance.
Hard to say which came first, the fatigue or the stress, but you have to deal with both.
Often stress is caused by our inappropriate response to stimuli, and changing this behaviour can lead to a reduction in stress generation.
Learn to say no, allow things to go wrong, just accept things you can't change-that sort of thing.
Try to look at yourself when next confronted with a potential strssor, and note what your first reaction is. If it is to fight it, see if you can work on flight instead.
Everyone has stressors to deal with, you just have to learn the least damaging way.

With fatigue, this may be a sign of a deeper problem, and it warrants further investigation.
I'd suggest that you start to list all of your symptoms, using top quality websites, and then see your doctor.
To give you an idea of the scope that you need to encompass, have a look at this symptom list for M.E.
Not saying this is what you have; it's just a helpful tool to research your problems better.
http://www.hfme.org/themesymptomlist.htm